This invention relates to valves used in automotive fuel systems in combination, for example, with a fuel pump, and more particularly, to a ported pressure relief valve (PPRV) mounted in the fuel path between the pump and fuel rail (for fuel injected engines) or a carburetor to provide a constant vapor purge when the engine is running, and to provide a means of allowing vapor to escape when the engine is off.
In conventional fuel systems, fuel is drawn from a fuel tank or reservoir into a low pressure inlet of an electric fuel pump. High pressure fuel from an outlet of the fuel pump is then delivered to the engine through a fuel rail. In some systems, unused fuel is directed back to the tank or reservoir through a return portion of the rail. Also in some systems, excess fuel flow is used to power a jet pump which is used to fill a reservoir in the fuel tank or the fuel pump module. The fuel system design must accommodate for a number of operational problems with the system including excess fuel flow, maintaining adequate pressure in the fuel lines even when the engine is off, thus preventing over pressures in the fuel delivery system resulting from a “hot soak”.
Each of these problems requires different solutions. Excess fuel pressure must be controlled so as not to cause engine flooding and to maintain efficient fuel delivery. Adequate pressure and/or liquid fuel must be maintained in the fuel lines, even though the engine and fuel pump are off, so when the engine is cranked, it will readily start. On the other hand, too much pressure can build up in the fuel system. This can occur during heat soak where the engine is turned off after running, and significant engine heat or ambient heat is transferred to the fuel lines through radiation, convection, or conduction. If an over pressure condition is not prevented, seals, fuel line connections, etc., may be compromised as is the subsequent fuel delivery capability of the system.
Individual valves and even combinations of valves and piping have been used in fuel systems to address these considerations. Examples of these are shown in U.S. Pat. Nos. 6,189,513, 5,715,798, 5,673,670, and 5,477,829. While use of these individual and combination valves address the various problems discussed, the number of components required adds significant cost to the fuel delivery system. It would be helpful to provide a single, relatively low cost device which is responsive to each of the above noted system concerns. Such a device would have the advantage of simplifying fuel system design and lowering its cost.